1. Technical Field
This invention generally relates to an apparatus for heating the air/fuel mixture entering the cylinders of an internal combustion engine. More particularly, the invention relates to a modular electric heater adapted for mounting within an intake passage of the engine.
2. Discussion
The air/fuel mixture entering the cylinders of an internal combustion engine is commonly heated to increase fuel economy and responsiveness to starting as well as to decrease pollutant discharge. One type of intake heating device generally includes a pair of gaskets surrounding a heating coil or grid disposed between the carburetor and the air intake manifold as shown in U.S. Pat. No. 4,020,812 to Hayward and U.S. Pat. No. 4,106,454 to Henlis. The gaskets in these devices prevent air leaks into and out of the engine manifold and thermally and electrically isolate the grid from the intake structure. However, as recognized and addressed in U.S. Pat. No. 5,595,164 ("the '164 Patent"), entitled "Low Profile Intake Manifold Heater", issued Jan. 21, 1997, gasket wear or aging may eventually short the electric circuit through the heating element.
While the heater of the '164 Patent addresses the short circuiting concerns, it uses a large mounting structure that supports the heating element within the manifold. This mounting structure is expensive to ship to customers, cumbersome to work with, and requires external gaskets to seal against the manifold. In addition to the manufacturing and shipping costs associated with the mounting structure, the requisite gaskets increase the overall joint thickness and the difficulty of constructing a joint that will both seal and provide structural support to the intake system.
In view of the above concerns as well as manufacturers' ever present desire to reduce manufacturing costs and complexity, a need exists for a modular heater device that may be easily and inexpensively manufactured, shipped, and installed in a variety of applications.